NASA's Kepler mission has provided a legacy data set for the study of stars and their planets. Kepler's high precision measurements reveals stellar brightness variations caused by oscillations of standing sound waves inside the stars. Just like the sound of a violin and a bass are different due to their different size, the Stellar Oscillations Group led by Dennis Stello uses observed frequencies of stellar oscillations to determine the sizes and masses of stars and what they are made of. Using this technique -- called asteroseismology -- is currently revolutionizing stellar astrophysics.